We present Keck K-band observations of GX 17+2 which reveal a bright counterpart in the radio error circle of Deutsch et al. (1999), coincident with their star ``A''. These observations imply an amplitude of variability of ~25--40 between our measurements and the IR observations of Deutsch et al. (1999). However, quasi-simultaneous RXTE ASM

``Böhm-Vitense gaps,'' discontinuities in the color distribution of A-F type stars along the main sequence, have traditionally been attributed to the abrupt onset of strong convection (8000 K>=Teff>=6400 K) in stellar atmospheres and envelopes. Using the full spectrum of turbulence model to describe convective transport (Canuto, Goldman, &

A realistic simulation of the stellar system α Cen A+B as it would be seen by MONS satellite has been generated in the "MONS Time-series simulation and analysis Team". The simulation apparently includes all properties known of the stars, instrumental noise sources and sensitivity properties expected. We have been working with this data series

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Stokes profiles of sunspot penumbrae show distinct asymmetries, which point to gradients in the velocity field and in the magnetic field. We present spectropolarimetric measurements of the Stokes vector in the neutral iron triplet at 1564.8 nm taken with the Tenerife Infrared Polarimeter (TIP) at the German Vacuum Tower Telescope (VTT) in Tenerife

We present a spectrophotometric study of short-term optical variability in the quiescent black hole X-ray transient V404 Cyg focusing on two nights of Hα spectroscopy. We find significant variability, with both the Hα line and the continuum varying in a correlated way. This includes both dramatic flares lasting a few hours in which the line flux